Objective To investigate the clinical effect of high-dose vitamin C combined with FOLFOX6 chemotherapy for colorectal cancer. Method The clinical data of 58 patients with colorectal cancer admitted to Aviation General Hospital from April 2016 to September 2017 were retrospectively analyzed. According to the treatment methods they were divided into experimental group treated with high - dose vitamin C combined with FOLFOX6 chemotherapy n = 29 cases and control group treated with FOLFOX6 chemotherapy alone n = 29 cases . The effects of treatment adverse reactions and improvements in patients′ quality of life were compared between the two groups. Result The effective rate was 58. 6% in the experimental group and 44. 8% in the control group with statistically significant differences P<0. 05 . After treatment tumor marker carcinoembryonic antigen and tumor marker carbohydrate antigen 19-9 concentrations in 2 groups were significantly decreased after treatment P<0. 05 and the decrease in experimental group was more obvious than control group P<0. 05 . The adverse reactions of digestive tract reaction and bone marrow suppression were significantly reduced in the experimental group and the differences between the two adverse reactions were statistically significant P< 0. 05 . The improvement rate of experimental group was 62. 06% which was significantly higher than that of control group 48. 27% and the difference was statistically significant P< 0. 05 . Conclusion Compared with FOLFOX6 chemotherapy alone high - dose vitamin C combined with FOLFOX6 chemotherapy in the treatment of colorectal cancer can achieve significant clinical efficacy reduce the adverse reactions of chemotherapy and improve the quality of life of patients which has high clinical value.